In recent years, liquid crystal display devices are used in various mobile devices such as smartphones, personal digital assistants (PDAs), and tablet computers. Generally, a liquid crystal display device includes a liquid crystal display panel, and a surface light source which is overlaid on the rear surface of the liquid crystal display panel for illumination. The surface light source may be, for example, a backlight unit which includes a reflective layer, light guide plate, optical sheet, light source such as LED, and rectangular resin frame. The reflective layer, light guide plate, and optical sheet are layered to overlap and are fitted in the resin frame. That is, the peripheries of the reflective layer, light guide plate, and optical sheet are maintained and positioned by the resin frame.
The resin frame is fixed to the liquid crystal display panel by a double-sided tape or an adhesive agent, and the backlight unit is positioned in line with the liquid crystal display panel. The liquid crystal display panel has a display area and a frame-shaped non-display area (frame area) around the display area. The resin frame of the backlight unit is fixed to the frame area of the liquid crystal display panel by a double-sided tape.
Size reduction of the frame area is greatly demanded to meet the requirement of enlargement of the display area. The frame area of the liquid crystal display panel is thus reduced more and more. However, the reduced frame area means that the area for the double-sided tape is reduced as well, and the area of the double-sided tape will not be sufficient. That is, sufficient adhesion of the resin frame will be difficult to secure.
Furthermore, when the backlight unit is manufactured thinner, the resin frame needs to be manufactured thinner as well. In that case, the durability of the resin frame decreases, and an assembly operation of optical sheets with such a thin resin frame becomes difficult.